Many abnormal medical conditions in humans and other mammals have been associated with disease and other aberrations along the lining or walls that define several different body spaces. In order to treat such abnormal conditions of the body spaces, medical device technologies adapted for delivering various therapies to the body spaces using the least invasive means possible.
As used herein, the term “body space,” including derivatives thereof, is intended to mean any cavity within the body which is defined at least in part by a tissue wall. For example, the cardiac chambers, the uterus, the regions of the gastrointestinal tract, and the arterial or venous vessels are all considered illustrative examples of body spaces within the intended meaning.
The term “vessel,” including derivatives thereof, is herein intended to mean any body space which is circumscribed along a length by a tubular tissue wall and which terminates at each of two ends in at least one opening that communicates externally of the body space. For example, the large and small intestines, the vas deferens, the trachea, and the fallopian tubes are all illustrative examples of vessels within the intended meaning. Blood vessels are also herein considered vessels, including regions of the vascular tree between their branch points. More particularly, the pulmonary veins are vessels within the intended meaning, including the region of the pulmonary veins between the branched portions of their ostia along a left ventricle wall, although the wall tissue defining the ostia typically presents uniquely tapered lumenal shapes.
One means of treating body spaces in a minimally invasive manner is through the use of catheters to reach internal organs and vessels within a body space. Electrode or electrophysiology (EP) catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity. In use, the electrode catheter is inserted into a major vein or artery, e.g., the femoral artery, and then guided into the chamber of the heart that is of concern in order to perform an ablation procedure.
U.S. Pat. No. 6,272,672 to Ben-Heim discloses the use of one or more piezoelectric elements or strain gages for generating signals indicative of bending about the axes of a catheter. While this patent discusses the use of such sensors for measuring and depicting the bend of the catheter to the user it does not provide a means for accurately providing force sensing at the tip of the catheter.
U.S. Pat. No. 6,612,992 to Rambow et al. discloses an ultrasound catheter that uses a plurality of strain gages placed along the periphery of the catheter to provide information regarding the position of the catheter in the cardiovascular system, however, there is no teaching with respect to sensing the force at the tip of the catheter.
As EP catheters are used in more procedures where tissue perforation is an issue, it would be desirable to have a tip electrode that provides more feedback such as force detection and tissue contact while having similar characteristics to existing EP catheter tips electrodes.
Furthermore, as EP catheters are used to ablate dynamically moving tissue, it will be necessary to have a catheter that accurately measures the force at the tip of the catheter while also having desirable deflection characteristics such as on-plane deflection.